Curettage of the endometrial lining of the uterus is often indicated to evaluate abnormal uterine bleeding. It is principally a diagnostic procedure to rule out pre-cancer and cancerous change. However, it does confer therapeutic effect in some cases. The lining of the uterus, known as the endometrium, responds to hormonal influences as part of the normal and abnormal endocrine patterns in females. The uterine lining undergoes proliferative change in response to estrogen or tamoxifen, secretory change in response to progestins, or atrophic change in the absence of all hormonal stimuli. During the natural cycle, in response to ovarian hormone secretion, the uterus undergoes proliferative response to estrogen, subsequently followed by a secretory response to estrogen plus progestin secretion. If pregnancy is not established, ovarian secretion of both the hormones declines resulting in sloughing of the endometrial lining, otherwise known as a menstrual period.
This endometrial cycling begins with menarche and ceases with menopause. Various conditions during the premenopausal and postmenopausal years cause the uterine lining to undergo abnormal proliferative changes requiring diagnostic intervention through curettage of the endometrium. The traditional surgical intervention known as dilatation and curettage (D&C) involves dilatation of the cervical canal and curetting of the endometrial lining of the uterus. Dilatation is accomplished using progressively wider uterine sounds to permit insertion of the uterine curettes.
In the United States the nearly universal practice is to perform the curettage with Sims curettes, which range from 7 to 10 mm in diameter. The average diameter of the non-gravid cervical canal measures less than 4 mm in diameter. Consequently, with Sims curettes the cervical canal requires dilatation to about twice its average non-gravid diameter. To accomplish dilatation of the cervix, a substantial force must be applied along the longitudinal axis of the cervical canal when passing the uterine sounds. This requires application of a tenaculum to the periphery of the cervix to apply the necessary countertraction. This dilatation procedure is exquisitely painful in the majority of unanesthetized patients because of the high concentration of stretch receptors in the cervix.
The curettage is accomplished by inserting the curette within the uterine cavity to the fundus, applying force to the curette blade in a direction perpendicular to the uterine wall, dragging the curette in a longitudinal fashion from the fundus to the lower uterine segment, and then out the cervical canal. The longitudinal forces applied during a curettage place the broad ligaments, cardinal ligaments, and uterosacral ligaments on stretch. The pain accompanying the longitudinal forces applied during curettage likely results from stretching the broad ligament, cardinal ligaments, and uterosacral ligaments. The suspensory ligaments of the uterus and cervix are enervated via fibers following the sympathetic nervous system pathways. Due to the diffuse origin of these pain fibers, it is difficult to anesthetize the suspensory ligaments with local techniques. Therefore, most women require some level of monitored anesthesia to accomplish this procedure.
Anesthetic techniques to relieve the pain in ascending order of effectiveness include IV sedation, paracervical block, regional anesthesia such as epidural or spinal block, and general anesthesia. With the limited effectiveness of IV sedation and paracervical block, and the prolonged recovery time associated with regional anesthesia, the vast majority of D&Cs are accomplished by general anesthesia. Eliminating the dilatation procedure could circumvent the need for monitored anesthesia. The combination of both dilatation and curettage generally precludes having only local anesthetic intervention.
Up to the present time, the D&C has been considered the "gold standard" for gynecological intervention for the diagnosis of endometrial disease states. With its ability to remove the vast majority of the endometrium, the D&C provides accurate diagnostic sensitivity. The procedure unfortunately requires the expense of outpatient surgical facilities and monitored anesthesia. Attention has been focused on developing instruments that are equal to, or of better diagnostic accuracy, but do not require cervical dilatation lending themselves to inexpensive and convenient office procedures.
As far back as the 1930s, beginning with Drs. Novak and Randall, office devices consisting of 1 to 4 mm stainless steel curettes, with either a smooth oval aperture or an elongated aperture with serrated edges, were proposed for office endometrial sampling. Although several favorable studies have been reported regarding their success in obtaining adequate samples, the technique was limited by relying on rigid stainless steel, which does not lend itself to conforming to the normal anatomic curves of the uterine cavity. This results in greater manipulation and discomfort. In addition, the adequacy of the sampling thoroughness is limited by poor suction techniques, using glass or plastic syringes attached to the proximal end.
Subsequently, in 1970, Jensen and Jensen marketed the Vabra.RTM. aspirator available from Berkeley Medevices, Inc., 907 Camelia Street, Berkeley, Calif., 94710, consisting of a 3 mm stainless steel cannula with a crescent shaped aperture at the distal end coupled with a mechanical suction pump providing a continuous suction. A number of studies show that its diagnostic sensitivity may approach that of D&C. However, the device has fallen in popularity today because it is much more painful than more recently developed techniques.
With the advent of plastic, a number of new curettes have been introduced to the market ranging in diameter from 2 to 4 mm. They fall into one of two design groups. First, the distal end of the cannula either has a small wedge taken out of the plastic resulting in a crescent shaped aperture at the distal most end of the opening, the aperture is simply a round hole in the cannula at the distal end, or consists of a linear port. The other design variance is the source of the suction, either an internal piston exists within the cannula which can be withdrawn, thereby creating a vacuum within the cannula or the hollow cannula is attached to a mechanical suction source. Berkeley Medevices has expanded their line of Vabra.RTM. aspirator cannulas to include plastic 4 mm cannulas with the either wedge shaped aperture or linear port. Another company in the market of aspirators with mechanical suction is the Mylex Tissue Trap Series from Mylex Products, 5915 Northwest Highway, Chicago, Ill., 60631, that have 2 and 3 mm stainless, as well as 3 to 7 mm flexible plastic, 3 to 7 mm semi-rigid, and 8 to 12 mm rigid plastic cannulas.
The latest devices consist of 3 mm plastic cannulas with an internal piston for suction, and a round hole aperture near the distal end of the cannula. First to be introduced in the United States is the Pipelle de Cornier.TM. which was developed in France and marketed in the United States as Pipelle.RTM. by Unimar Corporation, 475 Danbury Road, Wilton, Conn., 06897. Other companies have produced nearly identical instruments with minor variations on the theme regarding the type of plastics used and the specific design of the internal piston rod. One such device is the subject of the U.S. Pat. No. 5,069,224 issued to Zinnanti, Jr., and discloses an endometrial sampler that obtains small bits or portions of endometrium by aspiration without cutting, but rather avulsing the tissue sample.
Other examples include: the Gyno Sampler by GynoPharma, Inc., 50 Division Street, Somerville, N.J., 08876, having a product code 164-25; the Endocell by Wallach Devices, Inc., 291 Pepe's Farm Road, Milford, Conn., 06460; and the Endosampler by Medgyne Products, Inc., 328 North Eisenhower Lane, Lombard, Ill., 60148. These devices are manipulated by an in and out motion with concurrent rotation, and the endometrium is aspirated into the round aperture. The device is then withdrawn from the uterus along the longitudinal axis while the aspirated tissue remains within the cannula. These devices address the problems associated with the need for cervical dilatation associated with the traditional curettage with Sims Curettes.
The limitation of these devices is that they rely on a very small aperture to remove only a small portion of the endometrium. Additionally, the mechanical action is simply one of aspiration only at the site where the port comes in contact with the endometrial lining. An article by Rodriguez in American Journal of Obstetrics and Gynecology, January 1993, indicates that only four percent of the endometrial lining is removed even when the Pipelle.RTM. is used in sequence three times. By comparison, the Vabra.RTM. aspirator is more thorough, removing approximately 42 percent of the uterine lining. However, both techniques are far from removing the vast majority of endometrium provided by a traditional D&C. Consequently, these devices have substantial risk for missing endometrial disease such as hyperplasia or cancer. By only removing a small portion of endometrium, these devices preclude realizing any possible therapeutic gain by removing the substantial majority of the dysfunctional endometrial lining.
It would be desirable to have a device that would be capable of removing substantially all of the endometrium avoiding the risk of missing an important diagnosis, without causing a significant amount of pain and discomfort because of dilatation of the cervix and traction, tugging and pulling on the uterus.